1. Field of the Invention
The present invention relates in general to a glass plates positioning device for use in a laminated glass manufacturing line, and more particularly, to a positioning device for positioning two overlapped glass plates of different sizes, which are used for producing a warped laminated glass, such as a vehicular windshield or the like.
2. Description of the Prior Art
The laminated glass widely used as a safety glass comprises two sheets of plate glass with an interposal of a sheet of transparent resinoid, viz., interlayer which is glued to the two glass plates.
In manufacturing the laminated glass, two flat glass plates and a sheet of resinoid are preliminarily assembled as a sandwich, and the flat laminate is then led into a furnace to unite. During the heating, a suitable pressure is applied to the laminate to warp or curve the same. In order to allow the finished laminated glass, which is thus warped, to have a substantially matched edge, the two flat glass plates have different sizes. That is, the glass plate for the outer layer of the warped laminated glass is larger than the glass plate for the inner layer. Thus, before subjecting to the warping process, the two overlapped glass plates are compelled to have a continuous gap about the peripheries thereof. That is, as is understood from FIGS. 4 and 5, the overlapping is so made that the smaller glass plate is placed over the larger glass plate having the periphery thereof located somewhat inside of the periphery of the larger glass plate.
In order to achieve positioning of the overlapped glass plates before the warping process, one positioning device has been proposed, which is shown in Japanese Patent Second Provisional Publication No. 54-21846.
The positioning device of this publication comprises cylindrical pushing rollers, each being arranged vertically. In operation, the rollers are biased to abut, with their cylindrical side surfaces, against four sides of the overlapped glass plates which are conveyed to a furnace by a belt conveyer.
However, due to its inherent construction, the positioning device of the publication can position only a larger glass plate. In fact, the positioning device can not position a smaller glass plate placed on the larger glass plate, because the cylindrical outer surfaces of the pushing rollers do not reach the sides of the smaller glass plate. When the overlapped glass plates are subjected to the warping process with the smaller glass plate poorly positioned, they tend to break or have undesirable bubbles in the interposed resinoid sheet when they are temporarily pressed by tacking rolls and/or fully pressed in an autoclave.